Structural and lithological interpretation of aero-geophysical data in parts of the Lower Benue Trough and Obudu Plateau, southeast Nigeria

Ekwok, Stephen E.; Akpan, Anthony E.; Achadu, Ogiji-Idaga M.; Eze, Ohara E.

doi:10.1016/j.asr.2021.05.019

Cited by 18 publications

(7 citation statements)

References 42 publications

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“…These igneous invasions were detected by SPI and St-ED (Figure 4), as well as analytic signal and upward continuation enhancements (Figure 8). Geologic structures caused by intrusions in such regions are the potential pathway for hydrothermal fluid migration and mineralization in rift environments [18,34,64,[77][78][79] like the Bornu Basin. However, Figure 8b revealed E-W anticlinal structures (red-pink colour) adjoined by a trough-like structure (lemon green-blue colour) located at the southern and northern parts of the study area, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The 10th generation Inte national Geomagnetic Reference Field (IGRF) version 4.0 was applied by FAS on the com piled dataset to remove IGRF. In magnetic data reduction practice, IGRF, which is easil available and universally accepted, provides consistency in data reduction procedure [60 Processed and corrected high-resolution aero-magnetic data are very appropriate for min eral evaluation programs, basin framework, hydrocarbon, and hydrogeological explora tions, and delineation of the regional geologic boundary [26,[61][62][63][64][65][66][67]. The airborne magnet data employed in this investigation were corrected and processed to a total magnetic in tensity map (Figure 3) which were gridded, saved, and displayed in Oasis Montaj Geoso in colour raster format.…”

Section: Data Acquisitionmentioning

confidence: 99%

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Depth Estimation of Sedimentary Sections and Basement Rocks in the Bornu Basin, Northeast Nigeria Using High-Resolution Airborne Magnetic Data

et al. 2022

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This study involves the use of high-resolution airborne magnetic data to evaluate the thicknesses of sedimentary series in the Bornu Basin, Northeast Nigeria, using three depth approximation techniques (source parameter imaging, standard Euler deconvolution, and 2D GM-SYS forward modelling methods). Three evenly spaced profiles were drawn in the N-S direction on the total magnetic intensity map perpendicular to the regional magnetic structures. These profiles were used to generate three 2-D models. The magnetic signatures were visually assessed to determine the thickness of depo-centres and the position of intrusions. The thicknesses of sedimentary series based on source parameter imaging results are approximately ranged 286 to 615 m, 695 to 1038 m, and 1145 to 5885 m for thin, intermediate, and thick sedimentation, respectively. Similarly, the standard Euler deconvolution result shows thin (130 to 917 m), intermediate (1044 to 1572 m), and thick (1725 to 5974 m) sedimentation. The magnetic model of Profile 1, characterized by two major breaks, shows that the igneous intrusions and basement rocks are covered by sediments with thickness varying from 300 to <3500 m, while Profile 2 has a maximum estimated depth value of about 5000 m at the southern part. Furthermore, the Profile 3 model shows sediment thicknesses of 2500 and 4500 m in the northern and southern flanks of the profile, respectively. The maximum sediment thickness value from the various depth estimation methods used in this study correlate relatively well with each other. Furthermore, the anomalous depth zone revealed by the 2D forward models coincides with the locality of the thick sedimentation revealed by the source parameter imaging and standard Euler-deconvolution (St-ED) methods. The maximum depth values obtained from the various depth estimation methods used in this study correlated strongly with each other. The widespread occurrence of short-wavelength anomalies in the southern part of the study area as indicated by the jagged nature of the magnetic signature was validated by the analytic signal and upward-continuation results. Generally, it was observed that the southern part of the research area is characterized by thick sedimentation and igneous intrusions.

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Section: Discussionmentioning

confidence: 99%

Section: Data Acquisitionmentioning

confidence: 99%

Depth Estimation of Sedimentary Sections and Basement Rocks in the Bornu Basin, Northeast Nigeria Using High-Resolution Airborne Magnetic Data

et al. 2022

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“…On the whole, magnetic method provides a quick way of exploring depocentres, estimating sediment thicknesses, assessing mineralised areas (Ekwok et al, 2021a;2020a), delineating horst and graben structures (Ekwok et al, 2021b), as well as geothermal systems/structures (Abraham et al, 2019). Also, it is reported that geologic structures determine the location, concentration, and pattern of hydrothermal mineralization (Eldosouky and Elkhateeb, 2018), polymetallic anomalies, Copper-Uranium mineralization (Ekwok et al, 2021c;Boadi et al, 2013) including, the character and orientation of groundwater movement (Ekwok et al, 2020b). Currently, reconnaissance hydrocarbon exploration, minerals and geothermal energy investigations in the inland basins of Southern of Nigeria are being conducted employing the recent high-resolution magnetic data.…”

Section: Introductionmentioning

confidence: 99%

Appraisal of the magnetic and geothermal anomalies of bornu basin northeast nigeria involving aero-magnetic data

Ekwok¹,

Achadu²,

Ugar³

et al. 2023

Glo Jnl Geo Sci

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The Bornu Basin in northeast Nigeria was studied using high-resolution airborne magnetic data with the objective of improving the reliability of mapped magnetic and geothermal anomalies, and depth solutions. Necessary enhancement operations like analytic signal (ASIG), upward continuation, depth assessment methods involving standard Euler deconvolution (SED) and source parameter imaging (SPI) as well as spectral analysis applying the centroid technique were applied. The middle and southern parts are dominated by high frequency anomalies as revealed by the ASIG map. Furthermore, the magnetic data, when upward continued to 5 km, revealed avalanche of deeply buried igneous intrusions that created near-surface magnetic sources and geologic structures. Maximum thicknesses of sedimentary series estimated from SED and SPI, are respectively ~5974.7 and ~5885.3 m. These values correlate correlated relatively well with depth to the top boundary (Zt) of ~6550 m obtained from the centroid technique. These depth estimates reveal sequence of thick sediments overlying igneous intrusions and falls under the prospective geothermal anomaly zones characterised by high geothermal gradient (GG) (>55 °C/km) and heat flow (HF) (>130 mW/m2) values. Areas characterised by high geothermal anomalies correspond to igneous intrusion-dominated shallow Curie point depths (CPD or Zb).

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“…Uranium is found in various accessory minerals, including brannerite ((U,Ca,Ce)(Ti,Fe) 2 O 6 ), carnotite (K 2 (UO 2 ) 2 (VO 4 ) 2 •2H 2 O), uranite (H 4 O 2 U), uraninite (UO 2 ), uranophane (Ca(UO 2 ) 2 (Si 2 O 3 •5H 2 O), apatite (Ca 5 (PO 4 ) 3 (OH,F,Cl)), sphene (or titanite, CaTiOSiO 5 ), pitchblende (U 2 O 5 .UO 3 ) and zircon (ZrSiO 4 ) and so on [8]. Traces of some of these elements have been reported in rocks [9], soils [10,11], and water [12] in parts of the area. Therefore, exposure to ionizing radiation in the area is unavoidable due to the abundance of primordial radionuclides in the environment and even in some consumer products (e.g., tobacco, fuels, and building materials) [13,14].…”

Section: Introductionmentioning

confidence: 99%

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

et al. 2022

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A gamma spectrometric analysis of rock samples collected from the Precambrian Oban Massif, southeastern Nigeria, was performed to determine some primordial radioelements’ activity concentrations: U-238, Th-232, and K-40, and their associated radiological hazards. The mean activity of the primordial radionuclides was determined to be 1073.06 ± 0.65, 160.74 ± 1.32, and 250.76 ± 0.91 Bq·kg−1 for 40K, 238U, and 232Th, respectively, showing that they are inhomogeneously distributed, with activity changing with the rock type and location. The activity concentrations are highest in biotite garnet schist, quartz diorite, and biotite gneiss rock domains. The mean values of the radiological hazards are 0.08 Bq·kg−1 (alpha index), 2.15 Bq·kg−1(gamma index), 2.06 Bq·kg−1(internal) and 1.63 Bq·kg−1 (external4.30 Bq·kg−1(representative level index6), 602.23 Bq·kg−1, (radium equivalent), 780 nGy·h−1 (total absorbed dose rate), 270.91 nGy·h−1 (indoor), 509.78 nGy·h−1 (outdoor), 624.99, 1329.07 and 1954.06 mSv·yr−1 (outdoor, indoor and total annual effective dose equivalent, respectively), 6448.40 (cumulative excess lifetime cancer risk) and 248.94–3761.47 Bq·kg−1 (annual gonadal dose equivalent). These results are higher than their various permissible limits (except at Ako Community) and suggest that rocks in the area may be unsuitable for constructing dwelling places. It is strongly advised that basic safety standards and precautionary measures recommended by the European Commission should be strictly adhered to while dealing with these rocks.

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Structural and lithological interpretation of aero-geophysical data in parts of the Lower Benue Trough and Obudu Plateau, southeast Nigeria

Cited by 18 publications

References 42 publications

Depth Estimation of Sedimentary Sections and Basement Rocks in the Bornu Basin, Northeast Nigeria Using High-Resolution Airborne Magnetic Data

Depth Estimation of Sedimentary Sections and Basement Rocks in the Bornu Basin, Northeast Nigeria Using High-Resolution Airborne Magnetic Data

Appraisal of the magnetic and geothermal anomalies of bornu basin northeast nigeria involving aero-magnetic data

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

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